whether iit madras a better option or iit delhi or bombay for preparatory courses.because at iit madras and kharagpur civil,mechanical ,electrical,aerospace,production,chemical,mettalurgy branches are also available but at iit delhiand bombaymain branches available are chemical and mettalurgy,production,aerospace.please tell the sequence i should fill during counselling also considering branches remaining vacant there.

Hi

If you are getting electrical in IIt Madras then thats a fine choice, but after that go for Chemical engg in IIT Delhi or Madras ,.

Your preference order should be , electrical (madras)>chemical(delhi)>chemical(bombay)>chemical(madras)>mechanical(madras)>production(delhi)>aerospace(bombay)>civil(madras).. and then the other choices. 

Chemical engg. is a really good branch and can fetch u a reasonably good package too, and has got  a good scope ahead.